Why Does My Body Hurt When It Rains
“””It is not so much a question of where we are going as how.”” — Henry David Thoreau
The pain you feel when it rains isn’t just your imagination. Decreasing pressure (which ushers in bad weather) means air presses less on our bodies. That allows tissues to swell slightly, and it’s possible the resulting enlargement of tissues irritates the joints. The same thing happens during a sneeze or laugh, but these activities produce far smaller amounts of water vapor than rain does. Also, with a sneeze or a laugh, the swelling occurs within seconds; with rain, it can last for hours. And finally, rain doesn’t cause inflammation like laughter or coughing does.
But why does this happen? There are several reasons why it might be uncomfortable to wear tight clothing, sit inside a closed car or walk through standing water. One theory blames the increased discomfort on the body’s natural reaction to cold temperatures. Another focuses on the way the body responds to moisture without warning. To understand what causes your body to hurt when it rains, let’s take a closer look at each one of them.
When it comes to cold temperatures, there are two main theories that explain how they increase pain after prolonged exposure. First, some people believe the decrease in temperature triggers an automatic response by the body to prepare itself for colder conditions. The second idea suggests that the drop in core temperature creates an energy crisis. When the body loses heat faster than it generates new warmth, its metabolism slows down. This, in turn, decreases oxygen flow to vital organs. In addition, because the blood vessels constrict to conserve heat, they also limit circulation to areas like skin and extremities. As a result, the fingers, toes and nose may experience greater pain from cold.
To test whether cold actually contributes to pain, researchers have conducted experiments using ice cubes. For example, in one study, subjects were exposed to either dry air or moist air containing 0 percent humidity. The dry-air group experienced no increase in pain, while those who breathed humidified air did report mild discomfort [sources: Linder et al., Nissl]. But because the cold air was only cooled to 10 degrees Fahrenheit (-12 degrees Celsius), it’s difficult to say whether such extreme cooling could ever occur naturally. Other studies suggest that changes in brain activity caused by cold temperatures play a bigger role in causing pain than changes in core temperature do.
In his book “”Pain Without Trigger Points,”” Dr. Robert J. Ledley proposes another explanation for why cold temperatures bring about pain. He says that the act of breathing cools the lungs and that the subsequent lack of warm, carbon dioxide-rich air flowing into them leads to hypercapnia, which stimulates nociceptors located near the lungs. These nociceptors send signals to the cortex of the brain indicating that something foreign has entered the lungs. The person then feels chest pains, shortness of breath and other symptoms associated with panic or fear. If the person keeps inhaling cold air, however, the nociceptor stimulation continues despite the fact that it’s already known what the lungs contain. Eventually, the brain becomes desensitized to the stimulus and stops sending out pain signals.
So if cold really doesn’t contribute to pain, why does it still cause headaches, chills, nausea and other discomforts in many people? Let’s explore that topic next.
Cold Weather and Pain: Your Immune System Is Involved Too
If you’ve spent any time outdoors during winter months, you know that the weather affects moods differently depending on season. Some people find springtime flowers beautiful, while others consider them ugly pests. Even scientists disagree over how seasonal affective disorder works. Several prominent psychiatrists believe that SAD results from circadian rhythms gone awry, while others think the problem lies in chemical imbalances.
One important issue that researchers haven’t yet settled is why cold weather hurts people more than warm weather does. A recent hypothesis states that the reason stems from differences between the immune systems of humans and animals. According to this theory, the effect of cold weather on humans is similar to that of parasites. Parasites attack their hosts’ internal organs and cause swelling, which makes it harder for the host to breathe. Similarly, when the outer layer of skin thins due to moisture evaporation, it leaves a gap that bacteria, fungi and viruses can easily enter. Once inside the body, they cause infections and inflame the lining of the gut and respiratory tract. Therefore, instead of providing insulation, the outer layer of skin helps protect against infectious invaders.
Parasites seem to trigger similar responses in mammals. For instance, mice infected with mousepox become lethargic and develop rashes. Scientists suspect that the virus lowers the mice’s ability to control water loss through sweating. Because water evaporates from the epidermis, the skin shrinks, leaving gaps that allow the virus to spread throughout the body. People infected with human papillomavirus (HPV) also suffer from chronic itching and skin sores called warts, which form under wet conditions. HPV attacks cells responsible for producing keratin, a protein that provides strength and elasticity to skin. Keratin filaments strengthen hair shafts too, which explains why balding men often get warts.
On the next page, learn about how moisture causes pain.
Human Papillomaviruses infect the squamous epithelium, which covers most of the body except for palms, soles and mucous membranes. Among all the types of HPV, 16 are linked to cancer. About 5 million Americans contract genital warts every year, mostly among young people.
Moisture and Pain: Why Rain Hurts
Rainfall brings about a number of complex reactions within the body, including the release of endorphins, prostaglandin E2 and dopamine. Endorphins are chemicals released by certain nerve endings. Prostaglandin E2 is a molecule produced by fat tissue that regulates the function of various parts of the immune system. Dopamine is a neurotransmitter that transmits messages between nerves, especially in the central nervous system. All three substances stimulate receptors found in the walls of blood vessels. Stimulation of these receptors relaxes smooth muscle, allowing it to expand. When rainfall dilutes bodily fluids, the amount of dissolved nutrients increases, triggering the production of these compounds.
Some experts believe that the pain you feel when it rains originates in the parasympathetic nervous system, which controls involuntary functions such as saliva production, pupil dilation and heart rate. Although the exact mechanisms involved aren’t fully understood, the parasympathetic system contains fibers that connect to pain receptors. Just as the sympathetic nervous system sends pain impulses toward the spinal cord, the parasympathetic system carries signals to the brain in order to relieve pain.
Other researchers point out that because the inner ear perceives sounds based on vibrations, the mechanical effects of rainfall must influence hearing. They argue that the sensitivity of the cochlea to sound waves depends partly upon the fluid pressure inside. During periods of low pressure, the fluid swells up, reducing the distance between adjacent fluid layers. Consequently, the cochlea senses sound frequencies better. But when external pressures rise, the fluid compresses and narrows the space between fluid layers. At this point, the cochlea registers sounds more accurately.
Regardless of which theory turns out to be correct, it’s clear that the combination of lowered pressure and sudden change in pressure produces painful sensations. Rainwater’s rapid fall initially pressurizes the spaces surrounding capillary beds, which are tiny structures composed of tiny tubes. Capillary beds transport interstitial fluid around the body as part of normal metabolic processes. However, when rainwater falls suddenly onto the capillaries, the pressure rises above the level necessary to maintain equilibrium. As a result, the fluid begins moving away from the capillaries. Fluid then accumulates in larger spaces, increasing hydrostatic pressure. Increased pressure forces liquid out of the spaces, creating negative pressure. Negative pressure pulls fluids back toward the capillaries, decreasing hydrostatic pressure. The cycle repeats until equilibrium once again prevails.
Although the process seems simple enough, this phenomenon can create problems for the body. Hydrostatics refers to the physical property of liquids that causes them to assume specific shapes when held upside down. In everyday life, hydrostats are rarely encountered. But when a large amount of rainwater suddenly pours into a confined area, the hydrostatics become noticeable. For example, when rainwater enters a swimming pool, the surface of the water spontaneously dips downward. Conversely, when the water level in a swimming pool drops, the surface automatically rises upward. This behavior occurs because water expands when it absorbs outside pressure and contracts when it releases that pressure.
The sudden influx of water into the airways creates a vacuum, which sucks the air from inside the mouth and throat. Swallowing air is usually harmless, but when the volume exceeds 2 liters per minute, it can lead to suffocation and death. So even though rainwater’s impact on the body is relatively minor compared to drowning, it can still be harmful.
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